Star snails

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Star snails
Halgerda batangas

Halgerda batangas

Systematics
Class : Snails (gastropoda)
Subclass : Orthogastropoda
Superordinate : Heterobranchia
Order : Hind gill snails (Opisthobranchia)
Subordination : Nudibranchia (Nudibranchia)
Partial order : Star snails
Scientific name
Doridacea
Thiele , 1931

The star snails (Doridacea) are a suborder of the nudibranch within the order hind gill snails . The small to large shellless snails that occur in all oceans are carnivores that feed on various sessile animals.

features

The star snails often have a flattened body and no appendages (cerata), but instead often have small nodules. There are sclerites in the skin . The snails have a pair of long antennae, the rhinophores , which are very sensitive to odor and flow . Like other nudibranch snails, star snails lack a mantle cavity and shell. The anus is located in the upper third of the back and is surrounded by a ring of external gills , on the often star-like shape of which the name of the snail is based.

The star snails mostly live on stony ground and eat sessile animals , depending on the species these are sponges , bog animals , sea ​​squirts or barnacles .

The star snails are hermaphrodites that mate with each other with their penises . Every animal produces eggs and sperm and has two female openings - the mouths of the vagina and fallopian tubes (oviduct) - and a male sex opening with the spermatic duct , into which the penis is withdrawn. A blister behind the vagina, the bursa, initially takes in the sperm of the sex partner. Sperm for the later internal fertilization of egg cells are stored in a second bladder, the seminal sac ( receptaculum seminis ). The fertilization takes place in an enlargement of the fallopian tube. The eggs are laid in clusters of thousands of egg capsules, from which Veliger larvae hatch. During their pelagic phase, these occasionally carry a tiny shell that is later lost, so that the metamorphosis creates a shell -less slug. An exception among the nudibranchs are some species from the Dendrodorididae family , in which there is a direct development, i.e. ready-made snails hatch.

Systematics

According to Bouchet and Rocroi (2005), star snails (Doridacea) include four superfamilies with fifteen families. Some species examples are also given:

literature

  • Luise Schmekel, Adolf Portmann: Opisthobranchia of the Mediterranean: Nudibranchia and Saccoglossa . Springer-Verlag, Berlin Heidelberg New York 1982. Subordo Doridacea Odhner, 1934 : pp. 56-140.
  • Adam Sedgwick, Joseph Jackson Lister, Sir Arthur Everett Shipley: A Student's Text-book of Zoology: Protozoa to Chaetognatha . S. Sonnenschein and Company, 1898. Doridioidea : p. 412.
  • Philippe Bouchet & Jean-Pierre Rocroi: Part 2. Working classification of the Gastropoda . Malacologia, 47: 239-283, Ann Arbor 2005, ISSN  0076-2997 .
  • Victor Millard: Classification of the Mollusca. A Classification of World Wide Mollusca . Rhine Road, South Africa 1997, ISBN 0-620-21261-6 .
  • Rudie H. Kuiter , Helmut Debelius : Nudibranchs of the world's oceans: 1200 species worldwide. Kosmos Verlag, Stuttgart 2007. ISBN 3-440-11133-4 .

Web links

Individual evidence

  1. ↑ Doridacea . WoRMS . Retrieved December 20, 2013.
  2. ↑ Jeffrey HR Goddard (2005): Ametamorphic direct development in Dendrodoris behrensi (Nudibranchia: Dendrodorididae), with a review of developmental mode in the family . Proceedings of the California Academy of Sciences 56 (19), pp. 201-211. ( Abstract, doc ( Memento of the original dated February 22, 2016 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this note. ) @1@ 2Template: Webachiv / IABot / zeus.calacademy.org